A conventional method of manufacturing a module in which multilayer filters are integrated with an optical fiber and optical waveguide is described next with reference to FIG. 9. First, optical fiber 20 is provisionally secured onto metal housing 23, and condenser lens 21 for focusing light diffused from optical fiber 20 and multilayer filter 22 are mounted. Then, an optical signal is fed from optical fiber 20a at the input side. The optical signal from optical fiber 20b at the output side is measured, such as by a power meter, to adjust the optical axis and achieve the maximum optical signal. After adjustment, condenser lens 21 and multilayer filter 22 are caulked and fixed onto metal housing 23.
Accordingly, optical axis adjustment is required at 4 points when manufacturing the conventional module in which multilayer filter 22 is integrated with an optical path: (1) Optical axis adjustment between input optical fiber 20a and condenser lens 21, (2) Optical axis adjustment between condenser lens 21 and multilayer filter 22, (3) Optical axis adjustment between multilayer filter 22 and condenser lens 21, and (4) Optical axis adjustment between condenser lens 21 and output optical fiber 20b. Operability is thus poor in the prior art.